So. Let me introduce you to my friend LORETA.

It’s not what you think. Although I do know a really nice woman named Loreta. A colleague from a ways back. But I digress. What I’m talking about is LORETA, with capitals. It’s poised to transform the field of neurofeedback completely.

LORETA stands for Low Resolution Electromagnetic Tomography – I know, the acronym doesn’t really work, but “LORETA” is way nicer than “LRET”. I mean, c’mon, you can’t even pronounce “LRET”. LORETA is what is known mathematically as an “inverse solution”. That is, it’s a means of mathematically reconstructing the source or sources of scalp-recorded EEG patterns, deep within the three-dimensional space inside the skull. That is, inverse solutions aim at identifying where in the brain the stuff is happening that is being picked up as electrical fields on the surface of the head. I’ll explain:

EEG in its raw form looks like this. Each electrode picks up a complex, oscillating signal from the brain tissue underneath it, and the oscillations are plotted across time, like this:

This is the EEG that neurologists read. Now, for the purposes of neurofeedback, we analyse the EEG waves into their component oscillating frequencies and compare the size (amplitude) and scalp distribution of those oscillations to a normative database. For the gentleman depicted here, who is in his thirties, the EEG waves contained an abundance of activity (relative to other people his age) in the range between about 12 and 14 cycles per second, or 12 to 14 Hz. In the database output, that looked like this:

The yellow and orange areas are where, on my client’s scalp, the brain waves at these particular frequencies exceeded the amplitude that is considered normal compared to the EEG of other people his age. Notice how there seems to be something going on in the back half his head, maybe a little more on the right side than the left.

Now, that already provides us with a lot of information—especially given accumulated clinical wisdom that says an overabundance of activity in this frequency range in the back of the head is associated with anxiety (this guy was very anxious). But it doesn’t tell us where exactly in the brain all that 12 to 14 Hz activity is really coming from.

That’s where LORETA comes in. The invention of a neuroscientist at the University of Zurich named Roberto Pascual-Marqui, LORETA is a mathematical solution that estimates—as it turns out with a high degree of accuracy—exactly where, in three dimensions deep within the brain, the source of the activity measured on the scalp is. So, in the case of my client, here’s a depiction of which part of the brain was producing the most deviant of activity at 13 Hz:

The LORETA analysis superimposes the estimated locations of activity onto a standard image of the brain, and allows us to spot the location of the abnormal activity with remarkable accuracy. The images shown here are likes slices made by a big saw (not to be all macabre about it): one horizontal, one vertical along the long axis of the brain (perpendicular to a line drawn between the ears) and one vertical, crossing the long axis of the brain at ninety degrees (parallel to a line drawn between the ears). This three-dimensional “slicing” of the brain is the way all imaging techniques work. It is, in fact, where the word tomographycomes from; literally from the ancient Greek, “slice-writing”. Here’s what the same information looks like on an image of a whole, intact brain:

What LORETA allows us to do, then, is to identify with increased spatial accuracy where the patterns of brain activity observable as scalp EEG originate. Rather than looking at a smeared map of activity spread across a wide area of scalp, we can see in three dimensions where that activity actually originates in the brain. From there we can make connections to our knowledge about what locations and networks in the brain are involved in what sorts of functions. In this case, the area producing the most aberrant 13-Hz activity is the right temporoparietal junction (TPJ), which is known to be involved in responding to stimuli that are unexpected, but that have special behavioral importance or salience to the individual. Taking this information, along with the symptoms and complaints with which the individual comes to us, we can identify the structures and networks most likely to be contributing to their problems.

So, LORETA allows us to see with more precision where the sources of scalp-recorded EEG really are in the brain, even if they’re buried quite deep in the cranial vault. Want to know something even cooler? Stay tuned…